选择性 AKT2 剪接产生缺乏疏水性基序调节区的蛋白质。

Alternative AKT2 splicing produces protein lacking the hydrophobic motif regulatory region.

机构信息

Biomedizinisches Forschungslabor, Medizinische Klinik 1, Universitätsklinik Frankfurt, Frankfurt, Germany.

German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), Heidelberg, Germany.

出版信息

PLoS One. 2020 Nov 30;15(11):e0242819. doi: 10.1371/journal.pone.0242819. eCollection 2020.

Abstract

Three AKT serine/threonine kinase isoforms (AKT1/AKT2/AKT3) mediate proliferation, metabolism, differentiation and anti-apoptotic signals. AKT isoforms are activated downstream of PI3-kinase and also by PI3-kinase independent mechanisms. Mutations in the lipid phosphatase PTEN and PI3-kinase that increase PIP3 levels increase AKT signaling in a large proportion of human cancers. AKT and other AGC kinases possess a regulatory mechanism that relies on a conserved hydrophobic motif (HM) C-terminal to the catalytic core. In AKT, the HM is contiguous to the serine 473 and two other newly discovered (serine 477 and tyrosine 479) regulatory phosphorylation sites. In AKT genes, this regulatory HM region is encoded in the final exon. We identified a splice variant of AKT2 (AKT2-13a), which contains an alternative final exon and lacks the HM regulatory site. We validated the presence of mRNA for this AKT2-13a splice variant in different tissues, and the presence of AKT2-13a protein in extracts from HEK293 cells. When overexpressed in HEK293 cells, AKT2-13a is phosphorylated at the activation loop and at the zipper/turn motif phosphorylation sites but has reduced specific activity. Analysis of the human transcriptome corresponding to other AGC kinases revealed that all three AKT isoforms express alternative transcripts lacking the HM regulatory motif, which was not the case for SGK1-3, S6K1-2, and classical, novel and atypical PKC isoforms. The transcripts of splice variants of Akt1-3 excluding the HM regulatory region could lead to expression of deregulated forms of AKT.

摘要

三种 AKT 丝氨酸/苏氨酸激酶同工型(AKT1/AKT2/AKT3)介导增殖、代谢、分化和抗凋亡信号。AKT 同工型在 PI3-激酶下游以及 PI3-激酶独立机制中被激活。在很大比例的人类癌症中,脂质磷酸酶 PTEN 和增加 PIP3 水平的 PI3-激酶的突变增加 AKT 信号。AKT 和其他 AGC 激酶具有依赖于催化核心之后保守的疏水性基序(HM)的调节机制。在 AKT 中,HM 与丝氨酸 473 和另外两个新发现的(丝氨酸 477 和酪氨酸 479)调节磷酸化位点连续。在 AKT 基因中,这个调节 HM 区域编码在最后一个外显子中。我们鉴定了 AKT2 的一种剪接变体(AKT2-13a),它包含一个替代的最后外显子,并且缺乏 HM 调节位点。我们验证了不同组织中 AKT2-13a 剪接变体的 mRNA 存在,以及 HEK293 细胞提取物中 AKT2-13a 蛋白的存在。当在 HEK293 细胞中过表达时,AKT2-13a 在激活环和拉链/转弯基序磷酸化位点被磷酸化,但特异性活性降低。对其他 AGC 激酶的人类转录组的分析表明,所有三种 AKT 同工型都表达缺乏 HM 调节基序的替代转录本,而 SGK1-3、S6K1-2 和经典、新型和非典型 PKC 同工型则不是这种情况。AKT1-3 的剪接变体的转录本排除 HM 调节区可导致 AKT 的失调形式的表达。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/da03/7703976/5a7d2802cad6/pone.0242819.g001.jpg

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